Prior Art
The most conventional type of brushes for direct current, "d.c.", motors is a straight brush. Examples of which are found in several U.S. Patents such as U.S. Pat. No. 5,006,747, entitled "Dynamoelectric Machine Brush Rigging and Method of Assembly". U.S. Pat. No. 4,596,941, entitled "Electric Motor", illustrates brushes affixed to spring levers resiliently mounted on the end wall of the motor. This is still a straight brush.
Another type of brush is called the hammer brush and is illustrated by U.S. Pat. No. 4,638,204 entitled "Hammer Brush Holder Assembly for a Commutator Motor" issued on Jan. 20, 1987 by Siemens Aktiengesellschaft. This brush is mounted in a brush holder that is pivoted to bring the brush into contact with the commutator. The brush is a curved to follow the pivoting arc of the moveable brush holder.
Summary of Invention
It is a principle advantage of the motor to reduce the overall height or width of the motor for applications wherein the motor length or width is an advantage.
It is another advantage of the motor maintain the pressure of the brushes on the commutator over the life of the motor.
It is still another advantage to provide a two speed, four pole motor wherein the brushes are substantially contained within the armature laminations.
It is still another advantage to provide curved or crescent shaped brushes and maintain brush pressure constant during the life of the brushes.
These and other advantages will become apparent in the following detailed description.
A direct current permanent magnet motor having a housing open at one end and having an aperture centrally located in the closed end supporting a bearing member. The end bell of the motor is adapted to enclose the open end of the housing. Centrally located in the end bell is a bearing means adapted to be aligned with the bearing member at the closed end of the housing. A spring means locates and maintains the bearing means in the end bell. An armature means which includes an armature shaft rotatably mounted in the bearing means at one end and the bearing member in the housing intermediate the ends of the shaft, a commutator mounted on the armature shaft, and an armature including armature windings.
A brush card means has at least one pair of diametrically opposed brush means each having a brush, is mounted in the end bell and positioned so that the brushes are in contact with the commutator. The brush card means comprises an electrically non-conductive base member having a central aperture with a diameter larger than the diameter of the commutator. The base member supports the at least one pair of brush means within its outer periphery. The brush means has an arcuate brush tube for retaining and guiding an arcuate brush. The brushes are each maintained in contact with the commutator by means of a torsion spring mounted to the base member for biasing each of the brushes in an arcuate direction toward the commutator.
In a second embodiment, there is illustrated a two speed, four pole motor wherein the brush card contains brushes for each speed within the periphery of the ring shaped armature. Thus this motor is also reduced in height or width.